<template>
  <div>
    <div>
      <el-tree
        :data="data"
        node-key="id"
        default-expand-all
        @node-drag-start="handleDragStart"
        @node-drag-enter="handleDragEnter"
        @node-drag-leave="handleDragLeave"
        @node-drag-over="handleDragOver"
        @node-drag-end="handleDragEnd"
        @node-drop="handleDrop"
        draggable
        :allow-drop="allowDrop"
        :allow-drag="allowDrag"
      >
      </el-tree>
    </div>
    <div>
      <i class="icon-jiankong" icon-sel></i>
    </div>
  </div>
</template>

<script>
export default {
  data() {
    return {
      data: [
        {
          id: 1,
          label: "一级 1",
          children: [
            {
              id: 4,
              label: "二级 1-1",
              children: [
                {
                  id: 9,
                  label: "三级 1-1-1",
                },
                {
                  id: 10,
                  label: "三级 1-1-2",
                },
              ],
            },
          ],
        },
        {
          id: 2,
          label: "一级 2",
          children: [
            {
              id: 5,
              label: "二级 2-1",
            },
            {
              id: 6,
              label: "二级 2-2",
            },
          ],
        },
        {
          id: 3,
          label: "一级 3",
          children: [
            {
              id: 7,
              label: "二级 3-1",
            },
            {
              id: 8,
              label: "二级 3-2",
              children: [
                {
                  id: 11,
                  label: "三级 3-2-1",
                },
                {
                  id: 12,
                  label: "三级 3-2-2",
                },
                {
                  id: 13,
                  label: "三级 3-2-3",
                },
              ],
            },
          ],
        },
      ],
      defaultProps: {
        children: "children",
        label: "label",
      },
    };
  },
  methods: {
    handleDragStart(node, ev) {
      console.log("drag start", node);
    },
    handleDragEnter(draggingNode, dropNode, ev) {
      console.log("tree drag enter: ", dropNode.label);
    },
    handleDragLeave(draggingNode, dropNode, ev) {
      console.log("tree drag leave: ", dropNode.label);
    },
    handleDragOver(draggingNode, dropNode, ev) {
      console.log("tree drag over: ", dropNode.label);
    },
    handleDragEnd(draggingNode, dropNode, dropType, ev) {
      console.log("tree drag end: ", dropNode && dropNode.label, dropType);
    },
    handleDrop(draggingNode, dropNode, dropType, ev) {
      console.log("tree drop: ", dropNode.label, dropType);
    },
    allowDrop(draggingNode, dropNode, type) {
      if (dropNode.data.label === "二级 3-1") {
        return type !== "inner";
      } else {
        return true;
      }
    },
    allowDrag(draggingNode) {
      return draggingNode.data.label.indexOf("三级 3-2-2") === -1;
    },
  },
};
</script>